JPH0365076A - Ultrasonic motor and manufacture of same - Google Patents

Abstract

PURPOSE:To improve a mechanical accuracy and to make the loading force of a spring to a rotor uniform by providing a central shaft, of which the collar provided with a protrusion on the outer periphery in the middle and vicinity is formed into an integral body from the same member of high tension steel, and a head mass composed of a light flexible material welded to the periphery of the collar of the central shaft. CONSTITUTION:A head mass 13 is composed of a light flexible material such as Al alloy casting and formed into an integral body with the periphery of the collar 18 of a central shaft 17a, 17b by welding. Its one end face is secured to the end face of a longitudinal vibrator 11 via insulator 16a and a rotor 20 is pressure-welded to the other end face of the head mass via sliding material 22. That is, the central shaft 17a, 17b and collar 18 are constituted from high tension steel into an integral body and the outer periphery of the collar 18 is further provided with a protrusion to be equipped with the head mass 13. Therefore, the head mass 13 is outputted to amplify its amplitude and to output power to the contact surface of the rotor 20 via the sliding material 22. Thus, the improvement of strength and the prevention of secular change fatigue failure, not to mention the improvement of mechanical accuracy, are made possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic motor and a method for manufacturing an ultrasonic motor, and particularly relates to an ultrasonic motor that is press-welded via a head mass to a stator having a piezoelectric vibrator that excites ultrasonic vibrations. The present invention relates to an ultrasonic motor that rotates a rotor to generate driving force, and a method of manufacturing the ultrasonic motor.

[Conventional technology]

This ultrasonic motor and its manufacturing method are based on a new principle of obtaining rotational force through ultrasonic vibration,
Compared to conventional electromagnetic motors based on the interaction of current and magnetic fields, they have completely different characteristics of lower speed and higher torque.

In other words, the torque per unit volume is much higher than that of an electromagnetic motor, and when used at low speeds, gearless and brakeless operation is possible.Moreover, the scallop is small and the static holding force of the rotor is large, which improves responsiveness. It has great advantages.

Various ultrasonic motors have been proposed so far, for example, p.
In the paper ``Ultrasonic motor using longitudinal-torsional compound vibration'' reported on pages 821-822, the structure of a motor that can obtain high torque with a small diameter is introduced.

FIG. 3 is a front view showing an example of such a conventional ultrasonic motor, with the right half cut in section.

As shown in Fig. 3, the conventional ultrasonic motor has a stator 6.
0, a head mass 63 and a stator 70. This stator 60 includes a longitudinal vibrator (hereinafter referred to as a vertical vibrator) 61 made of a laminated piezoelectric actuator, a Langevin type torsional vibration excitation piezoelectric element (hereinafter referred to as a torsional vibrator) 62, a head mass 63, metal block 64 and nut 65. A central axis 67a and an insulator 66a.

66b (hereinafter considered as part of the longitudinal vibrator 61), and is driven in a torsional resonance mode. Note that this longitudinal vibrator 61 is excited non-resonantly in a manner that matches the resonant frequency of the stator 60. Furthermore, in the operation of the transducer portion of the mechanical channel filter using a torsional mode, the stator 60 operates in a mode by torsional deformation of a round bar similar to the movement of wringing a rag, as is well known. Moreover,
The momentum of the stator 60 is further amplified by the head mass 63. Therefore, the end faces of the head mass 63 where the stator 60 and the rotor 70 come into contact can generate rotational forces in the clockwise and counterclockwise directions at the resonance frequency.

Here, a case will be described in which the rotor 70 is rotated counterclockwise. First, the stator 60, which has been tightened with a nut, applies counterclockwise rotational force to the rotor 70.
When the end face of the head mass 63 in contact with the rotor 70 deforms in the counterclockwise direction, a voltage is applied from another power source so that the vertical vibrator 61 stretches and deforms in the axial direction in synchronization with the torsional vibration. Radomas 63 is instantly and strongly pressed.

The friction force at this time allows the rotor 70 to obtain a large rotational force in the counterclockwise direction. Next, when the surface of the head mass 63 in contact with the rotor 70 rotates clockwise, the vertical vibrator 61 is contracted in the axial direction, temporally bringing the contact force between the rotor 70 and the head mass 63 to zero, and clockwise. The clutch functions to prevent the torsional vibration displacement of M') from being transmitted to the rotor 70. Therefore, the rotor 70 can be smoothly rotated counterclockwise by a series of operations of the torsional vibration of the stator 60 and the expansion and contraction vibration of the vertical vibrator 61 disposed in the stator portion.

On the other hand, when the rotor 70 is rotated clockwise, the stator 60 is simply excited at the torsional resonance frequency.
It is only necessary to change the phase of the longitudinal vibrator 61 that performs the clutch operation so that the phase is 180 degrees different from that in the case where the rotor 70 is rotated counterclockwise. In this case as well, the rotor 70 can rotate smoothly clockwise.

In addition, the head mass 63 is made of an Au alloy,
As is well known, the He1 alloy is a light and soft metal, and has properties that are physically light in mass, easy to bend, and easy to twist. Therefore, although this AA gold alloy is a material that easily transmits longitudinal and torsional vibrations and amplifies the vibrations depending on how it is used, it has a property of having low mechanical strength.

Furthermore, the above-mentioned longitudinal vibrator 61 and torsional vibrator 62 are both made of piezoelectric ceramic, but although this piezoelectric ceramic is extremely strong against compressive force, it has the property of being extremely brittle against tension. ing. Therefore, it is necessary to constantly apply a larger compressive bias stress to the nut 65 to the longitudinal vibrator 61 and the torsional vibrator 62. In addition, in order to transmit the rotation of the stator 60 to the rollers 70, it is essential that the head mass 63 and the rotor 70 are strongly pressed together, so the head mass 63 and the rotor 70 are connected using a strong coil spring 72 and It is pressed and held by a nut 73 via a pedestal 74 and a bearing 71. Furthermore, in order for the stator 60 to perform torsional vibration, the head mass 63 . The longitudinal vibrator 61 and the torsional vibrator 62 must be firmly coupled.

In short, the conventional ultrasonic motor has a longitudinal vibrator 61 and a torsional vibrator 62 connected to a head mass 63 by bolts.

[Problem to be solved by the invention]

The conventional ultrasonic motor described above uses a pole 67b to hold the head mass 63 and rotor 70 with a strong coil spring 72. However, such a holding mechanism was not possible due to poor precision of the female screw provided in the head mass 63).
There is a problem that b is tilted and the load on the rotor 70 becomes uneven, making it impossible to realize smooth motor rotation. Further, there is a problem in that it is structurally impossible to lock the screws and causes loosening.

In addition, it is difficult to achieve mechanical precision when connecting vertical and torsional resonators using bolts 67a due to the poor precision of the female thread provided in the head mass 63.
7a is tilted, and the load on the longitudinal vibrator 61 and the torsional vibrator 62 becomes uneven, resulting in a problem that the best vibration mode cannot be achieved. Furthermore, the above-mentioned screw locking is structurally impossible and causes loosening, or the expansion and contraction of the vertical vibrator 61 causes a reciprocating tensile load in the axial direction to be applied to the pole 67a, which is a structurally weak AA alloy material. There is a problem in that stress concentration occurs in the threaded portion of the head mass 63, which may cause fatigue failure.

Therefore, as an ultrasonic motor with a vibration resonator, not only does the mechanical degree of freedom increase when there are many screw fastening points, but there is also the problem of damage to the female threads of the head mass 63, which is made of a weakly strong AA alloy material. be.

The purpose of the present invention is to improve these mechanical precisions, make the spring load force on the rotor uniform, and furthermore, make it easier to lock the screws and eliminate the loosening of the screws, and to prevent changes in characteristics over a long period of time. An object of the present invention is to provide a stable and highly reliable ultrasonic motor and a method of manufacturing the ultrasonic motor.

[Means to solve the problem]

The ultrasonic motor of the present invention includes a stator of a vertical and torsional composite piezoelectric vibrator, a head mass that transmits vertical and torsional vibration modes, a rotor that receives vertical and torsional vibrations and rotates in forward and reverse directions, and the stator and rotor. In an ultrasonic motor consisting of a central shaft that is tightened by sandwiching the head mass, a collar with a protrusion on the outer periphery near the middle is made of the same member force 11 made of high-tensile steel.
The head mass is made of a light and soft material and is welded around the flange of the central shaft.

In addition, in the method of manufacturing an ultrasonic motor of the present invention, an intermediate layer is formed by plating a composite material of high-tensile steel material and light soft material around the flange of the central shaft having protrusions on the outer periphery, and then The center shaft is heated to a high temperature so that the collar of the center shaft can be inserted into a container whose volume is slightly larger than the head mass, and then the light soft material is melted and poured into the container, and then cooled to remove the center shaft. It is configured to be hardened and fixed around the collar of the shaft to form an integral structure.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front view of the right half of an ultrasonic motor showing an embodiment of the present invention in cross section, and FIG. 2 is a front view of the integrated central shaft shown in FIG. 1.

As shown in FIGS. 1 and 2, in this example,
Stator 10 represents a nut-tight stator portion capable of outputting displacements in both longitudinal and torsional directions. For example, the ring-shaped piezoelectric element 12 (torsion vibrator) made of a piezoelectric material such as zirconium titanate-based piezoelectric ceramic,
All are circumferentially polarized. These piezoelectric elements are firmly laminated and bonded using an organic adhesive such as epoxy, solder, etc., with an electrode plate 12a made of Cu or the like interposed therebetween.

Furthermore, each of the -plates is polarized in opposite directions. That is, if the 1st and 3.5th stages are polarized clockwise, the 2nd, 4th and 6th stages are polarized counterclockwise. Further, electrodes are applied to the upper and lower surfaces by a method such as sputtering, plating, or vapor deposition, and electrical terminals are taken out in parallel. Therefore,
Based on the well-known principle of a torsional oscillator, in a torsional vibration conversion section made up of more layers of piezoelectric elements, the polarization directions of adjacent piezoelectric elements are opposite to each other. Furthermore, 11 is a ring-shaped laminated piezoelectric actuator (vertical vibrator), which is electrically insulated from the torsional vibration element 12 by insulators 16a and 16b.

The head mass 13 is made of a light and soft material such as AA alloy casting, and is integrally welded around the collars 18 of the central shafts 17a and 17b. One end face is fixed to the end face of the vertical vibrator 11 via an insulator 16a, and the other end face is pressed into contact with a rotor 20 via a sliding member 22. That is, the central shafts 17a, 17b and the collar 18 are integrally made of high-tensile steel, and the outer periphery of the collar 18 is provided with a head mass 13 with a protrusion. Therefore, the head mass 13 amplifies the amplitude of the output from the longitudinal vibrator 11 and the torsional vibrator 12, and outputs the amplified amplitude to the contact surface of the rotor 20 via the sliding member 22. In addition, the metal block 14 has a central axis 17a and a nut 15 that apply static pressure to the vertical vibrator 11.
This is provided to uniformly apply the voltage to each part of the torsional vibrator 12 and the insulators 16a and 16b.

On the other hand, the rotor 20 has a cylindrical shape, a bearing 21 is provided in the cylinder, and the rotor 20 is rotatably supported with a degree of freedom in the axial direction with respect to the central axis 17b. Furthermore, the force that presses the end surface of the rotor 20 against the stator 10 is transmitted by the spring 23 via the pedestal 25 and the bearing 21. The sliding material 22 described above has excellent wear resistance and is bonded to the end surface of the head mass 13.

In order to enable the ultrasonic motor to operate, the stator 10 and rotor 20 must be pressed against each other with strong static pressure when not in operation.

That is, the central axis 17b, the spring 23. The nut 24 and the pedestal 25 form a static pressure applying means, and in particular, the pedestal 25 is pressed against the end face of the inner ring of the bearing 21, and the rotor 20 is pressed against the outer ring of the bearing 21. Therefore, when the rotor 20 rotates, the member serving as the static pressure applying means does not rotate.

As is clear from the above-mentioned ultrasonic motor #I, the stator 10 operates in a mode of torsional deformation of a round rod similar to the movement of wringing a rag. By the way, the nut 15 and the central shaft 17a need to be completely fastened because the loosening, deformation, etc. of the nut 15 can significantly change the characteristics. Therefore, the insulator 16a and the longitudinal vibrator 11 are attached to the central axis 17a.
, the insulator 16b, the support plate 30, the torsional oscillator 1.2, and the metal block 14 are inserted in this order and firmly adhered to the end face of the head mass 13 with an organic adhesive such as epoxy or solder, and then tightened with a nut 15. The elliptical movement of the press-welded head mass 13 is adjusted to an optimal state, and the center shaft 17a and the joint threaded portion n1 of the nut 15 are melted and fixed at several points around the joint threaded portion by spot welding. In this case, spot welding can be performed by electric spot welding in addition to laser spot welding.

Further, since the rotor 20 is subjected to the elliptical movement of the end face of the heradomas 13', the rotor 20 rotates due to the frictional force thereof.

Therefore, it can be seen that the force with which the rotor 20 is pressed against the end surface of the head mass 13 significantly affects the characteristics.

Therefore, it is necessary to optimally adjust the pressing force using the nut 24 to completely fix the nut 24 to the shaft 17b. Therefore, in the same way as tightening the nut 15 of the stator 1o,
It is more effective to melt and fix the joint thread part n2 of the joint thread part 7b and the nut 24 by spot welding at several points around the joint thread part.

Next, a method for manufacturing an ultrasonic motor according to the present invention will be explained.

As shown in FIGS. 1 and 2, central axes 17a, 17
As mentioned above, the body of the b and the tsuba 18 is made of high-tensile steel, and the outer periphery of the tsuba 18 is provided with a protrusion in the form of a diamond-shaped knurl by machining to form the head mass 13.
Even if an external force is applied from the head mass 13 and the shafts 17a, 17b, the protrusions act as a wall to prevent misalignment, thereby preventing misalignment. The head mass 13 is made of a light and soft material such as aluminum alloy casting and is fixed around the central shafts 17a, 17b and the collar 18 by welding. This welding is first performed on the center shafts 17a, 17b and the collar 18 at a high temperature of about 600 to 700°C, and the head mass 13 and the alloy material of high tensile strength steel are plated and brought into a diffusion state to form an intermediate layer on the surface. . Furthermore, the central axis 17a.

17b and a flange 18, and which has an internal volume slightly larger than the head mass 13, a central shaft 17a,
17b and the collar 18 are set, and the material for the head mass 13 is melted and poured at a high temperature of about 600 to 700° C., and cooled while blending with the intermediate layer to form the central shaft 17a.

17b and collar 18 are firmly fixed. In addition, in the method described above, the deformation of the member is possible due to raising the temperature of the member, so higher precision can be achieved by making the member slightly larger in advance and performing final finishing such as machining after the head mass 13 is fixed. be able to.

〔Effect of the invention〕

As explained above, the ultrasonic motor of the present invention and its manufacturing method integrate the head mass by welding it to the central shaft, eliminating the need for screw fastening and improving the accuracy of the perpendicularity and concentricity between the head mass and the shaft. At the same time, since the pressure contact force is equalized, rotational fluctuations are minimized, which has the effect of increasing efficiency and increasing torque.

Further, by unifying the central axis, the present invention not only improves mechanical precision but also has strong strength and is effective in preventing aging and fatigue failure.

Furthermore, the present invention makes it possible to easily lock the screws by locating the screw fastening portions on the outside, which has the effect of eliminating parts that cause stiffness in the member structure and making it possible to stabilize the screws with a mechanically rigid body. There is.

[Brief explanation of drawings]

Fig. 1 is a front view of the right half of an ultrasonic motor showing an embodiment of the present invention in cross section, Fig. 2 is a front view of the integrated central shaft shown in Fig. 1, and Fig. 3 is a conventional example. FIG. 2 is a front view of the right half of the ultrasonic motor shown in section. 10... Stator, 11... Longitudinal vibrator, 12... Torsional vibrator, 13... Head mass, 14... Metal block, 15.24・
...Natsuto, 16a. 16b...Insulator, 17a, 17b...
・Central shaft, 18...Brim, 20...Rotor, 21...Bearing, 22...Sliding material, 23...Spring , 25... pedestal,
30...Support plate, nl, n2...Threaded part.

Claims (2)

[Claims] (1) A stator of a vertical and torsional composite piezoelectric vibrator, a head mass that transmits vertical and torsional vibration modes, a rotor that rotates in forward and reverse directions in response to vertical and torsional vibrations, and the stator and rotor are placed on both sides of the head mass. In an ultrasonic motor, the ultrasonic motor consists of a central shaft for tightening, a central shaft having a flange with a protrusion on the outer periphery near the middle integrally formed from the same high-tensile steel material, and a light soft material welded around the flange of the central shaft. An ultrasonic motor characterized by having a head mass consisting of: (2) In the method for manufacturing an ultrasonic motor according to claim (1), an intermediate layer is formed by plating a composite material of high-tensile steel material and light soft material around the collar of the central shaft having a protrusion on the outer periphery. Next, the central shaft is heated to a high temperature in a container whose internal volume is slightly larger than the head mass so that the collar of the central shaft can be inserted, and then the light soft material is melted and poured into the container, and then cooled. A method of manufacturing an ultrasonic motor, characterized in that the periphery of the flange of the central shaft is hardened and fixed to form an integral structure.